This invention relates to a steering gear of hydraulically driven vehicles having a pair of independently driven hydrostatic transmissions.
Steering of the hydraulically driven vehicles is made by controlling or manipulating a pair of hydrostatic transmission systems which drive the left and right side running gears to forward drive, deceleration, stopping and backward drive positions by the left and right side steering members, respectively.
For example, if one of the left and right side steering members is operated to stop one of the pair of hydrostatic transmission systems, the other hydrostatic transmission system is still rendered operative so that the vehicle can turn slowly or make a pivot turn. If the above-mentioned one of the steering members is operated further, said one of the hydrostatic transmission systems is shifted from stopping position to backward drive position so that the vehicle can turn quickly or make a spin turn.
Such steering operation system is, however, disadvantageous in that, while one of the hydrostatic transmission systems is under backward drive control, there is a possibility that the other hydrostatic transmission system is manipulated by the driver by mistake to backward drive position so as to cause an unexpected backward drive of the vehicle.